Rivet for welded electrical connections



Jan. 17, 1967 R. G. MAWNEY ETAL 3,299,239

RIVET FOR WELDED ELECTRICAL CONNECTIONS Original Filed June 6, 1960 2Sheets-Sheet 1 Fly. 1.

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A zg' United States Patent 3,299,239 RIVET FOR WELDED ELECTRICALCONNECTKONS Robert G. Mawney, Louis C. Beggs, and Robert A. Re-

naud, Attleboro, Mass; said Mawney and said Beggs assignors to TexasInstruments Incorporated, Dallas, Tex., a corporation of DelawareContinuation of application Ser. No. 97,409, Mar. 17, 1961, which is adivision of application Ser. No. 34,043, June 6, 1960. This applicationJan. 25, 1965, Ser. No. 436,977

Claims. (Cl. 200-166) This application is a continuation of ourcopending application, Serial No. 97,409, filed March 17, 1961, and nowabandoned, and entitled, Electrical Connections and Methods of MakingSame, which in turn is a division of Serial No. 34,043, filed June 6,1960. This invention relates to thermostatic devices, and in particular,to improved means and methods of making electrical connections to suchdevices.

It is one object of the instant invention to provide a simple andlow-cost means for electrically connecting an electrically conductivemember to a thermostatic element.

It is another object of the instant invention to provide a simple,economical and low-cost means for electrically connecting anelectrically conductive member to a thermo static element which does notupset or deleteriously affect the calibration of the thermostaticelement.

Other objects will be in part apparent and in part pointed outhereinafter.

The invention accordingly comprises the elements and combinationst ofelements, steps and sequence of steps, features of construction andmanipulation, and arrangements of parts, all of which will beexemplified in the structures and methods hereinafter described, and thescope of the application of which will be indicated in the followingclaims.

In the accompanying drawing, in which one of the various possibleembodiments of the invention is illus trated:

FIG. 1 is an exploded elevational view illustrating an electricalconnection between parts, according to the instant invention;

FIG. 2 is a view taken on line 22 of FIG. 1;

FIG. 3 is a view similar to FIG. 1, showing the parts in final assembledrelation;

FIG. 4 is a sectional view taken on line 4-4 of FIG. 3; and

FIG. 5 is atop plan view showing a snap-acting thermostatic discprovided with electrical connections according to the present invention.

Similar reference characters indicate corresponding parts throughout theseveral views of the drawings.

Referring now to FIG. 1, there is illustrated the means and techniquefor electrically connecting an electrically conductive member, forexample, a lead or pigtail 100, to a thermally responsive member suchas, for example, a thermostatic disc 22. Thermally responsive member 22may, for example, be an inherently snap-acting thermostatic disc orelement of the type described in the Spencer United States Patent No.1,448,240 or the Vander Pyl et al. United States Patent No. 2,694,121.Snap-acting element 22 may include a deformed or dished portion 24 (asbest seen in FIG. 5) which is responsible for its snap action. As iswell known in the art, such snap-acting elements are snappable inresponse to temperature change (for example, due to heating thereof uponthe flow of a current overload therethrough) from a first position ofrelative stability to a second position of relative stability, and uponcooling thereof, the element (if of the automatic reset type) will snapfrom said second position back ice to said first position. It will beunderstood that the thermostatic disc, prior to being electricallyconnected to lead or pigtail 100, will have been calibrated, or at leastinitially calibrated, prior to assembly of the latter into an electricalswitch, such as that disclosed in our copending parent applicationreferred to above.

It is a general object of this invention to connect the electricallyconductive member in permanent electrical connection with thethermostatc element or disc 22, but to accomplish this without upsettingor deleteriously shifting the calibration of the disc.

It has been found that when the electrically conductive member orpigtail is welded directly to the thermostatic or bimetallic disc orelement itself, there is an attendant deformation of the thermostaticdisc due to the very high heat concentration which undesirably anddeleteriously shifts the disc calibration. Further, many times thethermostatic bimetal of the disc is of very thin gauge, and does notprovide sufficient means or mass for welding purposes.

We have discovered that the features illustrated in FIGS. 1-4, to bedescribed below, advantageously obviate these problems, and additionallypermit electrically securing a pigtail or electrically conductive memberto the thermostatic element, even when such is of a very thin gauge,without deleteriously shifting or affecting the calibration thereof.

Thermostatic element 22 is provided with an aperture (which may bespaced from the nondevelopable or dished portion of the disc) which isadapted to loosely receive shank 202 of rivet 204. Rivet 204 isconveniently formed of a good, electrically conductive, readily weldablematerial, such as steel or Monel.

Rivet 204 (as best seen in FIGS. 1 and 2) includes a plurality ofdiamond or conical shaped projections 206. Pigtail or electricallyconductive member 100 is provided with a welding cap 210, which may besecured thereto as by crimping (see FIG. 4). Rivet 204, thermostaticelement 22, pigtail 100 and welding cap 210 are assembled in the mannershown in FIG. 1. Shank 202 is disposed within aperture 200, with diamondor conical points 206 in engagement with the undersurface 214 ofthermostatic element 22, as shown in FIG. 3. Aperture 200 is somewhatlarger than shank 202, so that the latter may be loosely confined withinthe former and to preclude contact therebetween. Shank 202 further is ofsuch a height as to protrude or project beyond the outer surface ofthermostatic element 22 when the rivet 204 is disposed within theaperture 200 and diamond points 206 are in engagement with surface 214of thermostatic element 22. The problems of deleteriously shifting thecalibration of the thermostatic disc during welding of an electricalconductor to the disc are advantageously eliminated by the instantinvention. The rivet 204 is initially welded to the thermostatic element22, for example, by resistance welding. The diamond points 206 serve asthe weld points and fixedly secure the rivet 204 to the thermostaticelement 22 in good electrical connection therewith. It is to be notedthat the welding of the rivet to the thermostatic bimetal generallytakes place prior to deformation of the thermostatic material to providethe dished portion and disc element and also prior to calibration of thedisc element. It will be noted that the only areas of contact betweenthe rivet 204 and the thermostatic bimetal element 22 are at the weldprojection points 206. Shank 202 is disposed in aperture 200 and ismaintained out of engageand temperature setting of the thermostatic disc22, the latter can be incorporated into its assembly, for example, suchas the subassembly 20 described in the aforesaid parent application forelectrical switch 10, and thereafter the pigtail or electrical lead 100may conveniently be welded and electrically secured thereto as will bedescribed below.

Pigtail 100 is electrically connected to thermostatic element 22 bywelding the cap 210 to the projecting portion of shank 202, as shown inFIGS. 3 and 4, as by resistance welding. During and after welding of thewelding cap 210 to the projecting part of shank 202, the latter ismaintained out of contact with and in spaced relation to the sidesurfaces of aperture 2% in thermostatic element 22. It is to beunderstood that during or after welding of the pigtail 100 to the shank202, there is some flow of material either from the shank 202 or thewelding cap, about the oversized disc hole 200, but not so much flow asto cause engagement or contact with the thermostatic element adjacent orabout the shank which might stress or deform the disc. It Will also benoted that after welding of the pigtail 100 to shank 202, the weldingcap 210 is maintained in spaced relationship with the upper surface ofthermostatic disc 22 to advantageously avoid stressing or deforming thedisc which might deleteriously shift or upset the calibration thereof.

It is to be understood that if desired, other types of weldingprojections may be provided instead of the diamond shaped projections206. For example, the welding projection might comprise a conventionalwelding ring. The important feature is that there be a minimum ofphysical contact between the thermostatic element and the rivet 204.Welding cap 210 serves the dual function of maintaining the strands orwires which comprise pigtail 100 into a dense mass and precludes themfrom unraveling during handling and welding and affords a constant anduniform area to weld to the projecting portion of shank 202 irrespectiveof the type of wire employed for the pigtail 100.

From the above it can be seen that the arrangement shown in FIGS. 1-4advantageously permits quickly and conveniently welding and electricallyconnecting a pigtail to the thermostatic disc Without changing ordeleterio-usly shifting the calibration thereof. It is to be noted thatthe only physical contact with the thermostatic element is through theweld point projections, which contact is made prior to calibration andformation of the disc.

It will be understood that by providing the thermostatic disc rivet 204,that a greater variety of types and sizes of pigtails can be welded tothe shank without affecting the temperature setting or calibration ofthe thermostatic disc 22, and affords a quick and low-cost method ofsecuring the pigtail electrically to the thermostatic element.

In view of the above, it will be seen that the several objects of theinvention are achieved and other advantageous results attained.

Dimensions of certain of the parts as shown in the accompanying drawinghave been modified for the purposes of clarity of illustration.

As many changes could be mad-e in the above constructions and methodswithout departing from the scope of the invention, it is intended thatall matter contained in the above description or shown in theaccompanying drawing, shall be interpreted as illustrative and not in alimiting sense, and it is also intended that the appended claims shallcover all such equivalent variations as come within the true spirit andscope of the invention.

It is to be understood that the invention is not limited in itsapplication to the details of construction and arrangement of partsillustrated in the accompanying drawing, since the invention is capableof other embodiments and of being practiced or carried out in variousways. Also it is to be understood that the phraseology or terminologyemployed herein is for the purpose of description and not of limitation.

We claim:

1. In combination: a snap-acting thermostatic element having a deformedportion therein responsible for its snap action; said thermostaticelement providing an aperture; an electrically conductive rivetincluding a shank portion; said rivet having a weld projection meansengageable with one side of said thermostatic element; said shankdisposed in said aperture and including a portion adjacent its free endprojecting beyond an opposite side of said thermostatic element and saidweld projection means; and an electrically conductive member welded tothe projecting portion of said shank adjacent and spaced from the saidopposite side of said thermostatic element, the aperture being largerthan the cross section of the shank portion such that the shank portionis substantially free from engagement with the portion of thethermostatic element defining the aperture.

2. The combination as set forth in claim 1 and wherein said weldingprojection means includes a plurality of spaced projecting points.

3. The combination as set forth in claim 1 and wherein said electricallyconductive member comprises a Wire lead; said wire lead being providedwith a Welding cap; and said welding cap being welded to the projectingportion of said shank.

4. In combination: a snap-acting thermostatic element having a deformedportion therein responsible for its snap action; said thermostaticelement providing an aperture; an electrically conductive rivetincluding a shank portion; said rivet having weld projectionv meansengageable with one side of said thermostatic element; said shankdisposed in said aperture and including a free end portion projectingbeyond a side of said thermostatic element opposite to said one side andadapted to be welded to an electrically conductive member; and saidaperture being sufficiently larger than the cross section of said shankwhereby when said rivet is welded to said thermostatic element andbefore said electrically conductive member is welded to said projectingfree end portion of said shank, said shank is substantially free fromengagement with the portions of said thermostatic element defining saidaperture.

5. The combination as set forth in claim 4 and wherein said weldingprojection means includes a plurality of spaced projecting points.

References Cited by the Examiner UNITED STATES PATENTS 5/1955 Tri-pp etal 219-93 X 6/1958 Epstein 200-438 ROBERT K. SCHAEFER, Primary Examiner.

1. IN COMBINATION: A SNAP-ACTING THERMOSTATIC ELEMENT HAVING A DEFORMED PORTION THEREIN RESPONSIBLE FOR ITS SNAP ACTION; SAID THERMOSTATIC ELEMENT PROVIDING AN APERTURE; AN ELECTRICALLY CONDUCTIVE RIVET INCLUDING A SHANK PORTION; SAID RIVET HAVING A WELD PROJECTION MEANS ENGAGEABLE WITH ONE SIDE OF SAID THERMOSTATIC ELEMENT; SAID SHANK DISPOSED IN SAID APERTURE AND INCLUDING A PORTION ADJACENT ITS FREE END PROJECTING BEYOND AN OPPOSITE SIDE OF SAID THERMOSTATIC ELEMENT AND SAID WELD PROJECTION MEANS; AND AN ELECTRICALLY CONDUCTIVE MEMBER WELDED TO THE PROJECTING PORTION OF SAID SHANK ADJACENT AND SPACED FROM THE SAID OPPOSITE SIDE OF SAID THERMOSTATIC ELEMENT, THE APERTURE BEING LARGER THAN THE CROSS SECTION OF THE SHANK PORTION SUCH THAT THE SHANK PORTION IS SUBSTANTIALLY FREE FROM ENGAGEMENT WITH THE PORTION OF THE THERMOSTATIC ELEMENT DEFINING THE APERTURE. 